1. Field of the Invention
This invention relates to an improvement in a digitizer for computer drafting and more particularly to a digitizer which is less cumbersome and less subject to error due to manufacturing variations. Furthermore, it can be moved across a drafting board to any desired position and then locked in that adjusted position.
2. Description of the Prior Art
In a conventional digitizer, a computer is provided in a fixed location on both the X beam and the Y beam and multiple wire connectors are attached thereto which extend from the computer to a readout display and keyboard. The display gives a visual indication of the position of the plotter attached to the Y beam and the position of the Y beam on the X beam. In other words, the exact point of the plotter will be visually displayed on the readout in response to a position sensing device associated with the computer. The computer is usually located at one end of each of the beams and the multiple wire connectors must be long enough to facilitate movement of the Y beam along the X beam to the opposite end of the X beam from the computer and similarly the multiple wire connectors in the Y beam must be long enough to facilitate movement of the plotter to the opposite end of the Y beam from the X beam. The problem in prior art devices is when the relative location of the beam and plotter is not at the extreme or extended position, the slack in the multiple wire connectors causes them to droop down and be both unsightly and in the way. Another difficulty is that the beams which are usually formed by extrusion are often warped in the extrusion process and the required tolerances are almost impossible to hold. Thus, the beam must be either made by more costly process or very carefully selected sections of extruded members must be made in order to find a section which is sufficiently straight to meet the required tolerances. Finally, brake means for releasably holding a plotter in adjusted position in prior art devices sometimes slip and are not as secure as required for accurate measurements.